Keysight Technologies N5511A, Руководство пользователя

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72 N5511A Phase Noise Test System User’s Guide
Absolute Measurement Fundamentals
Tracking Frequency Drift
Tracking Frequency Drift
The system’s frequency drift tracking capability for the phase lock loop
measurement is directly related to the tuning range of the VCO source being
used. The system’s drift tracking range is approximately 24% of the peak
tuning range (PTR) of the VCO.
PTR= VCO Tuning Constant X Voltage Tuning Range
This is the frequency range within which the beat note signal created by the
test set’s phase detector must remain throughout the measurement period. In
addition, the beat note signal must remain within the system’s Capture Range
(5% of the PTR) during the time it takes the system to calibrate and lock the
phase lock loop.
The stability of the beat note is a function of the combined frequency stability
of the sources being used for the measurement. If beat note drift prevents the
beat note from remaining within the Capture Range long enough for the
system to attain phase lock, the computer informs you by displaying a
message. If the beat note drifts beyond the drift tracking range during the
measurement, the computer stops the measurement and inform you that the
system has lost lock.